Systems and methods for treating vertebral bodies

ABSTRACT

Systems and methods treat at least two vertebral bodies in a spinal column. The systems and methods make use of first and second tool assemblies operable to treat an interior region of, respectively, a first vertebral body and a second vertebral body in the spinal column. The systems and methods provide directions for operating the first and second tool assemblies to treat the first and second vertebral bodies, at least for a portion of time, concurrently.

RELATED APPLICATION

This application is a continuation-in-part of U.S. patent applicationSer. No. 09/134,323, filed Aug. 14, 1998, now U.S. Pat. No. 6,241,734.

FIELD OF THE INVENTION

The invention generally relates to the treatment of bone conditions inhumans and other animals.

BACKGROUND OF THE INVENTION

The deployment of expandable structures, generically called “balloons,”into cancellous bone is known. For example, U.S. Pat. No. 4,969,888 and5,108,404 disclose apparatus and methods using expandable structures incancellous bone for the fixation of fractures or other osteoporotic andnon-osteoporotic conditions of human and animal bones.

SUMMARY OF THE INVENTION

The invention provides systems and methods for treating bone.

According to one aspect of the invention, the systems and methods treatat least two vertebral bodies in a spinal column. The systems andmethods make use of first and second tool assemblies operable to treatan interior region of, respectively, a first vertebral body and a secondvertebral body in the spinal column. The systems and methods providedirections for operating the first and second tool assemblies to treatthe first and second vertebral bodies, at least for a portion of time,concurrently.

According to another aspect of the invention, the systems and methodsemploy a device for compacting cancellous bone. The device comprises awall adapted to be inserted into bone and undergo expansion incancellous bone to compact cancellous bone. The systems and methodsinclude a cortical bone plugging material inserted into the bone eitherbefore or after expansion of the device.

According to another aspect of the invention, the systems and methodsinclude an instrument introducer defining an access passage intocancellous bone through cortical bone. The systems and methods alsoinclude an instrument including a distal body portion having a dimensionsized for advancement through the access passage to penetrate cancellousbone. In one embodiment, the instrument includes a proximal stop havinga dimension greater than the access passage and having a location toprevent penetration of the distal body portion beyond a selected depthin cancellous bone. In another embodiment, the distal body regionincludes a blunt terminus to tactilely indicate contact with corticalbone without breaching the cortical bone.

According to another aspect of the invention, the systems and methodsuse an instrument introducer defining an access passage into cancellousbone through cortical bone. A gripping device restes on an exterior skinsurface and engages the instrument introducer to maintain the instrumentintroducer in a desired orientation.

According to another aspect of the invention, the systems and methodsinclude a device adapted to be inserted into bone in a collapsedcondition and thereafter expanded to form a cavity in cancellous bone.The systems and methods employ a fluid transport passage to convey fluidfrom a source into the cavity to resist formation of a vacuum inside thecavity as the device is returned to the collapsed condition andwithdrawn from bone.

According to another aspect of the invention, the systems and methodsinclude a device adapted to be inserted into bone and undergo expansionin cancellous bone. A transport passage conveys an expansion medium intothe device. The expansion medium includes an amount of material toenable visualization of the expansion. The systems and methods includean exchanger assembly communicating with the transport passage andoperating to reduce the amount of material present in the expansionmedium within the device.

Another aspect of the invention provides systems and methods for formingan opening in cortical bone. In one embodiment, the systems and methodsemploy a support body including a flexible shaft portion. A corticalbone cutting element is carried on the flexible shaft portion. Theelement operates to form an opening in cortical body in response toapplication of force. In another embodiment, a cortical bone cuttingelement is carried on a support body to form an opening into the bone.An expandable structure also carried on the support body and adapted tobe inserted through the opening and expanded to form a cavity incancellous bone.

Features and advantages of the various aspects of the invention are setforth in the following Description and Drawings, as well as in theappended Claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a lateral view of a human spinal column;

FIG. 2 is a representative coronal view, with portions broken away andin section, of a human vertebral body, taken generally along line 2—2 inFIG. 1;

FIG. 3 is a lateral view, with portions broken away and in section, ofseveral vertebral bodies, which are part of the spinal column shown inFIG. 1;

FIG. 4 is a plan view of a tool which carries at its distal end anexpandable structure, which, in use, compresses cancellous bone, thestructure being shown in a collapsed condition;

FIG. 5 is enlarged side view of the expandable structure carried by thetool shown in FIG. 4;

FIG. 6 is a coronal view of the vertebral body shown in FIG. 2, with asingle tool shown in FIGS. 4 and 5 deployed through a lateral access ina collapsed condition;

FIG. 7 is a coronal view of the vertebral body and tool shown in FIG. 6,with the tool in an expanded condition to compress cancellous bone andform a cavity;

FIG. 8 is a coronal view of the vertebral body shown in FIGS. 6 and 7,with the tool removed after formation of the cavity;

FIG. 9A is a coronal view of the vertebral body shown in FIGS. 8, withthe cavity filled with a material that strengthens the vertebral body;

FIG. 9B depicts an alternate method of filling a cavity within avertebral body;

FIG. 9C depicts the vertebral body of FIG. 9B, wherein the cavity isapproximately half-filled with material;

FIG. 9D depicts the vertebral body of FIG. 9B, wherein the cavity issubstantially filled with material;

FIG. 10 is a coronal view of the vertebral body shown in FIG. 2, withtwo tools shown in FIGS. 4 and 5 deployed through bilateral accesses andin an expanded condition to compress cancellous bone and form adjoining,generally symmetric cavities;

FIG. 11 is a coronal view of the vertebral body shown in FIG. 10, withthe tools removed after formation of the generally symmetric cavitiesand the cavities filled with a material that strengthens the vertebralbody;

FIG. 12 is a coronal view of the vertebral body shown in FIG. 10, withthe tools removed after formation of generally asymmetric cavities;

FIG. 13 is a anterior sectional view of three adjacent vertebral bodies,with six tools shown in FIGS. 4 and 5 deployed in collapsed conditionsthrough two lateral accesses in each vertebral body;

FIGS. 14A to 14D are schematic anterior views of one of the vertebralbodies shown in FIG. 13, showing the alternating, step wise applicationof pressure to the expandable structures to compress cancellous bone andform adjacent cavities;

FIGS. 15A and 15B are schematic anterior views of one of the vertebralbodies shown in FIGS. 14A to 14D, depicting the alternating sequence offilling the adjacent cavities with a material to strength the vertebralbody;

FIGS. 16A to 16I are coronal views of a vertebral body as shown in FIGS.14A to 14D and 15A and 15B, showing tools deployed to create a lateralaccess to compress cancellous bone in a vertebral body to form aninterior cavity, which is filled with a material to strengthen thevertebral body;

FIG. 17 is an exploded side section view of a reduced diameter obturatorinstrument with associated centering sleeve, which can be deployed tocreate access in a vertebral body, particularly through a pedicle;

FIG. 18A is a side section view of a drill bit instrument that can bedeployed to create access to a vertebral body, the drill bit instrumenthaving a flexible shaft and deployed through a cannula instrument havinga deflected end;

FIG. 18B is a side view of a drill bit instrument that can be deployedto create access to a vertebral body, the drill bit instrument having aflexible shaft and deployed over a guide wire having a deflected end;

FIG. 18C is a side view of a drill bit instrument that can be deployedto create access to a vertebral body, the drill bit instrument having aflexible shaft and including steering wires to deflect its distal end;

FIG. 19 is a coronal view of a vertebral body showing the deployment ofa spinal needle tool in a manner that creates a breach in an anteriorcortical wall of the vertebral body;

FIG. 20A is an enlarged side view of a drill bit instrument having amechanical stop to prevent breach of an anterior cortical wall of thevertebral body;

FIG. 20B is an enlarged side view of a cortical wall probe that can bedeployed to gauge the interior dimensions of a vertebral body withoutbreaching an anterior cortical wall of the vertebral body;

FIG. 21 is coronal view of a vertebral body with an expandable structuredeployed and expanded, showing the introduction of a liquid to preventformation of a vacuum upon the subsequent deflation and removal of thestructure;

FIG. 22A is a side view of a tool to introduce material into a cavityformed in cancellous bone, with a nozzle having a stepped profile toreduce overall fluid resistance;

FIG. 22B is a side view of a tool to introduce material into a cavityformed in cancellous bone, with a nozzle having a tapered profile toreduce overall fluid resistance;

FIG. 22C is a side view of a tool to introduce material into a cavityformed in cancellous bone, with a nozzle having a reduced interiorprofile to reduce overall fluid resistance;

FIG. 23 are top views of kits which hold, prior to use, the variousinstruments and tools usable to create multiple access paths in a singlevertebral body, to compact cancellous bone and form a cavity to befilled with a material, as generally shown in FIGS. 16A to 16I;

FIGS. 24A to 24C are coronal views of a vertebral body, showing a smallexpandable body deployed through a needle to create a small cavity, andthe injection of a filling material under pressure through the needle tofill and enlarge the cavity to strengthen the vertebral body;

FIG. 25 is an enlarged side section view of an expandable body carriedat the end of a catheter tube, which further includes an integrateddrill bit instrument;

FIG. 26A is a perspective view of one embodiment of a locking device fora cannula instrument;

FIG. 26B is a perspective view of another embodiment of a locking devicefor a cannula instrument;

FIG. 27 is a perspective view of a composite tool that includes a trocarand a cannula instrument;

FIG. 28 is a perspective view of the composite instrument shown in FIG.27, with the trocar separated from the cannula instrument;

FIG. 29A is a perspective view of a hand engaging the composite handleof the tool shown in FIG. 27;

FIG. 29B is a perspective view of a hand engaging the handle of thecannula instrument when separated from the trocar;

FIG. 30 is a top view showing deployment of the composite instrumentshown in FIG. 27 in a vertebral body, by using the composite handle toapply an axial and/or torsional force;

FIG. 31 is a top view of the vertebral body, showing deployment of adrill bit through a cannula instrument, which forms a part of thecomposite tool shown in FIG. 27; and

FIG. 32 depicts an exchange chamber for replacing and/or diluting theradiopaque medium within a structure with a partially-radiopaque orradiopaque-free medium;

FIG. 33 is an exploded perspective view of a cannula and materialintroducing device, which embodies features of the invention.

The invention may be embodied in several forms without departing fromits spirit or essential characteristics. The scope of the invention isdefined in the appended claims, rather than in the specific descriptionpreceding them. All embodiments that fall within the meaning and rangeof equivalency of the claims are therefore intended to be embraced bythe claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This Specification describes new systems and methods to treat bonesusing expandable bodies. The use of expandable bodies to treat bones isgenerally disclosed in U.S. Pat. Nos. 4,969,888 and 5,108,404, which areincorporated herein by reference. Improvements in this regard aredisclosed in U.S. patent application, Ser. No. 08/188,224, filed Jan.26, 1994; U.S. patent application Ser. No. 08/485,394, filed Jun. 7,1995; and U.S. patent application Ser. No. 08/659,678, filed Jun. 5,1996, which are each incorporated herein by reference.

The new systems and methods will be described with regard to thetreatment of vertebral bodies. It should be appreciated, however, thesystems and methods so described are not limited in their application tovertebrae. The systems and methods are applicable to the treatment ofdiverse bone types, including, but not limited to, such bones as theradius, the humerus, the femur, the tibia, or the calcanus.

I. Vertebral Bodies

As FIG. 1 shows, the spinal column 10 comprises a number of uniquelyshaped bones, called the vertebrae 12, a sacrum 14, and a coccyx 16(also called the tail bone). The number of vertebrae 12 that make up thespinal column 10 depends upon the species of animal. In a human (whichFIG. 1 shows), there are twenty-four vertebrae 12, comprising sevencervical vertebrae 18, twelve thoracic vertebrae 20, and five lumbarvertebrae 22.

When viewed from the side, as FIG. 1 shows, the spinal column 10 formsan S-shaped curve. The curve serves to support the head, which is heavy.In four-footed animals, the curve of the spine is simpler.

As FIGS. 1 to 3 show, each vertebra 12 includes a vertebral body 26,which extends on the anterior (i.e., front or chest) side of thevertebra 12. As FIGS. 1 to 3 show, the vertebral body 26 is in the shapeof an oval disk. As FIGS. 2 and 3 show, the vertebral body 26 includesan exterior formed from compact cortical bone 28. The cortical bone 28encloses an interior volume 30 of reticulated cancellous, or spongy,bone 32 (also called medullary bone or trabecular bone). A “cushion,”called an intervertebral disk 34, is located between the vertebralbodies 26.

An opening, called the vertebral foramen 36, is located on the posterior(i.e., back) side of each vertebra 12. The spinal ganglion 39 passthrough the foramen 36. The spinal cord 38 passes through the spinalcanal 37.

The vertebral arch 40 surrounds the spinal canal 37. The pedicle 42 ofthe vertebral arch 40 adjoins the vertebral body 26. The spinous process44 extends from the posterior of the vertebral arch 40, as do the leftand right transverse processes 46.

II. Treatment of Vertebral Bodies

A. Lateral Access

Access to a vertebral body can be accomplished from many differentdirections, depending upon the targeted location within the vertebralbody, the intervening anatomy, and the desired complexity of theprocedure. For example, access can also be obtained through a pedicle 42(transpedicular), outside of a pedicle (extrapedicular), along eitherside of the vertebral body (posterolateral), laterally or anteriorly. Inaddition, such approaches can be used with a closed, minimally invasiveprocedure or with an open procedure.

FIG. 4 shows a tool 48 for preventing or treating compression fractureor collapse of a vertebral body using an expandable body.

The tool 48 includes a catheter tube 50 having a proximal and a distalend, respectively 52 and 54. The distal end 54 carries a structure 56having an expandable exterior wall 58. FIG. 4 shows the structure 56with the wall 58 in a collapsed geometry. FIG. 5 shows the structure 56in an expanded geometry.

The collapsed geometry permits insertion of the structure 56 into theinterior volume 30 of a targeted vertebral body 26, as FIG. 6 shows. Thestructure 56 can be introduced into the interior volume 30 in variousways. FIG. 6 shows the insertion of the structure 56 through a singlelateral access, which extends through a lateral side of the vertebralbody 12.

Lateral access is indicated, for example, if a compression fracture hascollapsed the vertebral body 26 below the plane of the pedicle 42, orfor other reasons based upon the preference of the physician. Lateralaccess can be performed either with a closed, mininimally invasiveprocedure or with an open procedure. Of course, depending upon theintervening anatomy, well known in the art, lateral access may not bethe optimal access path for treatment of vertebrae at all levels of thespine.

The catheter tube 50 includes an interior lumen 80 (see FIG. 4). Thelumen 80 is coupled at the proximal end of the is catheter tube 50 to apressurized source of fluid, e.g., saline. A syringe containing thefluid can comprise the pressure source. The lumen 80 conveys the fluidinto the structure 56 under pressure. As a result, the wall 58 expands,as FIGS. 5 and 7 show.

The fluid is preferably rendered radiopaque, to facilitate visualizationas it enters the structure 56. For example, Renografin™ can be used forthis purpose. Because the fluid is radiopaque, expansion of thestructure 56 can be monitored fluoroscopically or under CTvisualization. Using real time MRI, the structure 56 may be filled withsterile water, saline solution, or sugar solution, free of a radiopaquematerial. If desired, other types of visualization could be used, withthe tool 48 carrying compatible reference markers. Alternatively, thestructure could incorporate a radiopaque material within the material ofthe structure, or the structure could be painted or “dusted” with aradiopaque material.

Expansion of the wall 58 enlarges the structure 56, desirably compactingcancellous bone 32 within the interior volume 30 (see FIG. 7) and/orcausing desired displacement of cortical bone. The compaction ofcancellous bone 32 forms a cavity 60 in the interior volume 30 of thevertebral body 26 (see FIG. 8). As will be described later, a fillingmaterial 62 can be safely and easily introduced into the cavity 60 whichthe compacted cancellous bone 32 forms. In one embodiment, expansion ofthe structure 56 desirably forms a region of compacted cancellous bonewhich substantially surrounds the cavity 60. This region desirablycomprises a barrier which limits leakage of the filling material 62outside the vertebral body 26. In an alternate embodiment, the expansionof the structure 56 desirably presses cancellous bone 32 into smallfractures which may be present in cortical bone, thereby reducing thepossibility of the filling material 62 exiting through the corticalwall. In another alternative embodiment, the expansion of the structure56 desirably flattens veins in the vertebral body that pass through thecortical wall (e.g., the basivertebral vein), resulting in lessopportunity for filling material 62 to extravazate outside the vertebralbody through the venous structure in the cortical wall. Alternatively,expansion of the structure 56 will compress less dense and/or weakerregions of the cancellous bone, which desirably increases the averagedensity and/or overall strength of the remaining cancellous bone.

The compaction of cancellous bone by the structure 56 can also exertinterior force upon cortical bone. Alternatively, the structure 56 candirectly contact the cortical bone, such that expansion and/ormanipulation of the structure will cause displacement of the corticalbone. Expansion of the structure 56 within the vertebral body 26 therebymakes it possible to elevate or push broken and compressed bone back toor near its original prefracture position.

The structure 56 is preferably left inflated within the vertebral body26 for an appropriate waiting period, for example, three to fiveminutes, to allow some coagulation inside the vertebral body 26 tooccur. After the appropriate waiting period, the physician collapses andremoves the structure 56. As FIG. 8 shows, upon removal of the structure56, the formed cavity 60 remains in the interior volume 30.

As FIGS. 9B, 9C, and 9D show, the physician next introduces a fillingmaterial 62 into the formed cavity 60 using an appropriate nozzle 114(as will be described in greater detail later). The filling material 62(which FIG. 9A shows after its introduction into the cavity 60) cancomprise a material that resists torsional, tensile, shear and/orcompressive forces within the cavity 60, thereby providing renewedinterior structural support for the cortical bone 28. For example, thematerial 62 can comprise a flowable material, such as bone cement,allograft tissue, autograft tissue, or hydroxyapatite, synthetic bonesubstitute, which is introduced into the cavity 60 and which, in time,sets to a generally hardened condition. The material 62 can alsocomprise a compression-resistant material, such as rubber, polyurethane,cyanoacrylate, or silicone rubber, which is inserted into the cavity 60.The material 62 can also comprise a semi-solid slurry material (e.g., abone slurry in a saline base), which is either contained within a porousfabric structure located in the cavity 60 or injected directly into thecavity 60, to resist compressive forces within the cavity 60.Alternatively, the material 62 could comprise stents, reinforcing bar(Re-Bar) or other types of internal support structures, which desirablyresist compressive, tensile, torsional and/or shear forces acting on thebone and/or filler material.

The filling material 62 may also comprise a medication, or a combinationof medication and a compression-resistant material, as described above.

Alternatively, the filling material 62 can comprise a bone fillingmaterial which does not withstand compressive, tensile, torsional and/orshear forces within the cavity. For example, where the patient is notexpected to experience significant forces within the spine immediatelyafter surgery, such as where the patient is confined to bed rest orwears a brace, the filling material 62 need not be able to immediatelybear load. Rather, the filling material 62 could provide a scaffold forbone growth, or could comprise a material which facilitates oraccelerates bone growth, allowing the bone to heal over a period oftime. As another alternative, the filling material could comprise aresorbable or partially-resorbable source of organic or inorganicmaterial for treatment of various bone or non-bone-related disordersincluding, but not limited to, osteoporosis, cancer, degenerative diskdisease, heart disease, acquired immune deficiency syndrome (AIDS) ordiabetes. In this way, the cavity and/or filler material could comprisea source of material for treatment of disorders located outside thetreated bone.

In an alternative embodiment, following expansion, the expandablestructure 56 can be left in the cavity 60. In this arrangement, flowablefilling material 62 is conveyed into the structure 56, which serves tocontain the material 62. The structure 56, filled with the material 62,serves to provide the renewed interior structural support function forthe cortical bone 28.

In this embodiment, the structure 56 can be made from an inert, durable,non-degradable plastic material, e.g., polyethylene and other polymers.Alternatively, the structure 56 can be made from an inert,bio-absorbable material, which degrades over time for absorption orremoval by the body.

In this embodiment, the filling material 62 itself can serve as theexpansion medium for the structure 56, to compact cancellous bone andform the cavity 60, to thereby perform both compaction and interiorsupport functions. Alternatively, the structure 56 can be first expandedwith another medium to compact cancellous bone and form the cavity 60,and the filling material 62 can be subsequently introduced after theexpansion medium is removed from structure 56 to provide the interiorsupport function. As another alternative, the filling material couldcomprise a two-part material including, but not limited to, settablepolymers or calcium alginate. If desired, one part of the fillingmaterial could be utilized as the expansion medium, and the second partadded after the desired cavity size is achieved.

The structure 56 can also be made from a permeable, semi-permeable, orporous material, which allows the transfer of medication contained inthe filling material 62 into contact with cancellous bone through thewall of the structure 56. If desired, the material can comprise amembrane that allows osmotic and/or particulate transfer through thematerial, or the material can comprise a material that allows themedication to absorb into and/or diffuse through the material.Alternatively, medication can be transported through a porous wallmaterial by creating a pressure differential across the wall of thestructure 56.

As another alternative, fluids, cells and/or other materials from thepatient's body can pass and/or be drawn through the material into thestructure for various purposes including, but not limited to,fluid/cellular analysis, bony ingrowth, bone marrow harvesting, and/orgene therapy (including gene replacement therapy).

B. Bilateral Access

As FIGS. 10 and 11 show, an enlarged cavity 64, occupying substantiallyall of the interior volume, can be created by the deployment of multipleexpandable structures 56A and 56B through two lateral separate accessesPLA1 and PLA2, made in opposite lateral sides of a vertebral body 26. InFIG. 10, the expandable structures 56A and 56B are carried by separatetools 48A and 48B at the distal ends of catheter tubes 50A and 50B,which are separate and not joined together.

Expansion of the multiple expandable structures 56A and 56B forms twocavity portions 64A and 64B (shown in FIG. 11). The cavity portions 64Aand 64B are transversely spaced within the cancellous bone 32. Thetransversely spaced cavity portions 64A and 64B preferably adjoin toform the single combined cavity 64 (shown in FIG. 11), into which afilling material is injected.

Alternatively (not shown), the transversely spaced cavity portions 64Aand 64B can remain separated by a region of cancellous bone. The fillingmaterial is still injected into each cavity portion 64A and 64B.

FIG. 10 shows the structures 56A and 56B to possess generally the samevolume and geometry, when substantially expanded. This arrangementprovides a symmetric arrangement for compacting cancellous bone 32. Agenerally symmetric, enlarged cavity 64 (shown in FIG. 11) results.

Alternatively, the structures 56A and 56B may possess different volumesand/or geometries when substantially expanded, thereby presenting anasymmetric arrangement for compacting cancellous bone 32. A generallyasymmetric cavity 66 (see, e.g., FIG. 12) results.

The selection of size and shape of the structures 56A and 56B, whethersymmetric or asymmetric, depends upon the size and shape of the targetedcortical bone 28 and adjacent internal anatomic structures, or by thesize and shape of the cavity 64 or 66 desired to be formed in thecancellous bone 32. It can be appreciated that the deployment ofmultiple expandable structures 56A and 56B makes it possible to formcavities 64 or 66 having diverse and complex geometries within bones ofall types.

It has been discovered that compression fracture or collapse of onevertebral body can occur in combination with compression fracture orcollapse of an adjacent vertebral body or bodies. For example, thefailure of one vertebral body may alter loading of adjacent vertebralbodies, or can cause unequal loading of adjacent vertebral bodies,resulting in failure of one of more of the adjacent bodies as well.Because the factors which weaken and/or cause fracture of one vertebralbody will often weaken and/or affect other vertebral bodies within thespinal column, these adjacent vertebral bodies are susceptible tofracture and/or collapse. In a similar manner, the treatment of acompression fracture of a single vertebral body may alter the loading ofthe adjacent vertebral bodies, possibly resulting in failure of one ofmore of the adjacent bodies. The treatment of two or more vertebralbodies during a single procedure may therefore be indicated.

FIG. 13 shows a procedure treating three adjacent vertebral bodies 26A,26B, and 26C, each with bilateral accesses. As shown, the multiplebilateral procedure entails the deployment of six expandable structures56 (1) to 56 (6), two in each vertebral body 26A, 26B, and 26C. As FIG.13 shows, expandable structures 56(1) and 56(2) are bilaterally deployedin vertebral body 26A; expandable structures 56(3) and 56(4) is arebilaterally deployed in vertebral body 26B; and expandable structures56(5) and 56(6) are bilaterally deployed in vertebral body 26C.

The volume of a given cavity 64 formed in cancellous bone using multipleexpandable structures (e.g., using a bilateral or other type of access)can be optimized by alternating the expansion of the multiple expandablestructures deployed. For example, in the illustrated embodiment, in eachvertebral body, one of the expandable structures 56(1) is firstexpanded, followed by the expansion of the other expandable body 56(2).

When pressure is first applied to expand a given structure 56(1) to56(6), cancellous bone will begin to compact and/or cortical bone willbegin to displace. A period of time follows in which the pressure withinthe structure 56(1) to 56 (6) typically decays, as the cancellous bonerelaxes, further compacts and/or cortical bone is further displaced.Pressure decay in one structure also typically occurs as the otherexpandable structure within the vertebral body is expanded. Whenpressure is again restored to the structure 56(1) to 56(6), furthercancellous bone compaction and/or cortical bone displacement generallyresults. A further decay in pressure in the structure 56(1) to 56(6)will then typically follow. A decay of pressure will generally followthe application of pressure, until the cancellous bone is compacted adesired amount and/or cortical bone is displaced to a desired position.

Optimal cavity formation therefore occurs when each expandable structure56 (1) to 56 (6) is allowed to expand in a sequential, step wisefashion. By allowing the pressure in each structure to decay beforeintroducing additional pressure, the peak internal pressure experiencedwithin each structure can be reduced, thereby reducing the potential forfailure of the structure. FIGS. 14A to 14D more particularly demonstratethis step wise sequence of applying pressure to a given pair ofexpandable structures, e.g., 56(1) and 56(2), when deployed bilaterallyin a vertebral body 26A. It should be appreciated, that the step wiseapplication of pressure can also be used when a single expandable bodyis deployed, or when one or more expandable structures are deployed inother than in a lateral fashion, e.g., using a transpedicular,extrapedicular, or anterior access.

It should also be understood that expandable structures incorporatingnon-compliant materials could be used in similar manners to accomplishvarious objectives of the present invention. For example, where theexpandable structures comprise non-compliant materials, such structurescould be expanded within the cancellous bone in the previously describedmanner to compress cancellous bone, create a cavity and/or displacecortical bone. Depending upon the density and strength of the cancellousand/or cortical bone, the described application of additional pressureto the structures could cause a similar cycle of volumetric growth andpressure decay. Upon reaching maximum capacity and/or shape of thestructures, the introduction of additional pressure would typicallyresult in little volumetric expansion of the structures.

In FIG. 14A, the expandable structures 56(1) and 56(2) have beenindividually deployed in separate lateral accesses in vertebral body26A. The expandable structures 56(3)/56(4) and 56(5)/56(6) are likewiseindividually deployed in separate lateral accesses in vertebral bodies26B and 26C, respectively, as FIG. 13 shows. Representative instrumentsfor achieving these lateral accesses will be described later.

Once the expandable structures 56(1) to 56(6) are deployed, thephysician successively applies pressure successively to one expandablestructure, e.g., 56(1), 56(3), and 56(5), in each vertebral body 26A,26B, and 26C. FIG. 14A shows the initial application of pressure tostructure 56(1). Alternatively, the physician can deploy expandablestructures in a single vertebral body, expand those structures asdescribed herein, and then deploy and expand expandable structureswithin another vertebral body. As another alternative, the physician candeploy the expandable structures in a single vertebral body, expandthose structures as described herein, fill the cavities within thatvertebral body, and then deploy and expand expandable structures withinanother vertebral body.

The pressure in the structures 56(1), 56(3), and 56(5) will, over timedecay, as the cancellous bone in each vertebral body 26A, 26B, and 26Crelaxes, further compresses and/or cortical bone displaces in thepresence of the expanded structure 56(1), 56(3), and 56(5),respectively. As pressure decays in the structures 56(1), 56(3), and56(5), the physician proceeds to successively apply pressure to theother expandable structures 56(2), 56(4), and 56(6) in the samevertebral bodies 26A, 26B, and 26C, respectively. FIG. 14B shows theapplication of pressure to structure 56(2), as the pressure in structure56(1) decays.

The pressure in each structure 56(2), 56(4), and 56(6) will likewisedecay over time, as the cancellous bone in each vertebral body 26A, 26B,and 26C is compressed in the presence of the expanded structure 56(2),56(4), and 56(6), respectively. As pressure decays in the structures56(2), 56(4), and 56(6), the physician proceeds to successively applyadditional pressure to the other expandable structures 56(1), 56(3), and56(5) in the vertebral bodies 26A, 26B, and 26C, respectively. Theintroduction of additional pressure in these structures 26(1), 26(3),and 26(5) further enlarges the volume of the cavity portions formed as aresult of the first application of pressure. FIG. 14C shows theintroduction of additional pressure to structure 56(1) as pressuredecays in structure 56(2).

Pressure, once applied, will typically continue to decay in eachstructure 56(1)/56(2), 56(3)/56(4), and 56(5)/56(6), as the cancellousbone relaxes, continues to compact and/or cortical bone is displaced. Aspressure is successively applied and allowed to decay, the volumes ofthe cavity portions also successively enlarge, until desired cavityvolumes have been achieved in the vertebral bodies 26A, 26B, and 26Cand/or desired displacement of cortical bone has been achieved.

This deliberate, alternating, step wise application of pressure, insuccession first to the structures 26(1)/26(3)/26(5) and then insuccession to the structures 26(2)/26(4)/26(6) in the three vertebralbodies 26A/B/C continues until a desired endpoint for each of thevertebral bodies 26A, 26B, and 26C is reached. In one embodiment, thedesired cavity volume is achieved when cancellous bone is uniformly,tightly compacted against surrounding cortical bone. In an alternativeembodiment, desired cavity volume is achieved when a significantpressure decay no longer occurs after the introduction of additionalpressure, such as where substantially all of the cancellous bone hasbeen compressed and/or the cortical bone does not displace further.

It should be understood that compaction of cancellous bone may be nonuniform due to varying factors, including local variations in bonedensity. In addition, it should be understood that desired displacementof cortical bone can be accomplished in a similar manner, either aloneor in combination with compaction of cancellous bone. By utilizingmultiple structures to displace the cortical bone, a maximum amount offorce can be applied to the cortical bone over a larger surface area,thereby maximizing the potential for displacement of the cortical bonewhile minimizing damage to the cortical bone from contact with thestructure(s) and/or cancellous bone.

Once the desired volume for each cavity 64 and/or desired displacementof cortical bone in each vertebral body 26A, 26B, and 26C is reached,the physician begins the task of conveying a selected filling material62 into each formed cavity 64. It should be appreciated that thecavities 64 can be filled with filling material 62 essentially in anyorder, and it is not necessary that all expandable structures beexpanded to form all the cavities 64 before the filling material isconveyed into a given cavity.

In one embodiment, the filling material is conveyed in alternating stepsinto the cavity portions 64A and 64B of each vertebral body 26A, 26B,and 26C. In this technique, the cavity volumes 64A formed by theexpandable structures 56(1), 56(3), and 56(5) are filled in successionbefore the cavity volumes 64B formed by the expandable structures 56(2),56(4), and 56(6) are filled in succession.

FIGS. 15A and 15B show this embodiment of a filling sequence for thevertebral body 26A. The vertebral bodies 26B and 26C are filled in likemanner. In the vertebral body 26A, the expandable structure 56(1) isdeflated and removed. The filling material 62 is then conveyed into thecorresponding cavity portion 64A. Next, in the vertebral body 26B, theexpandable structure 56(3) is deflated and removed, and the fillingmaterial 62 conveyed into the corresponding cavity portion 64A. Next, inthe vertebral body 26C, the expandable structure 56(5) is deflated andremoved, and the filling material 62 conveyed into the correspondingcavity portion 64A. The expandable structures 56(2), 56(4), and 56(6)are left inflated within the respective vertebral bodies 26A, 26B, and26C during this portion of the filling process.

The physician waits for the filling material 62 conveyed into thevertebral bodies 26A, 26B, and 26C to harden. Then, as FIG. 15B showsfor the vertebral body 26A, the expandable structure 56(2) is deflatedand removed. The filling material 62 conveyed into the correspondingcavity portion 64B. Next, in the vertebral body 26B, the expandablestructure 56(4) is deflated and removed, and the filling material 62conveyed into the corresponding cavity portion 64B. Last, in thevertebral body 26C, the expandable structure 56(6) is deflated andremoved, and the filling material 62 conveyed into the correspondingcavity portion 64B. The above sequence allows a single batch of thefilling material 62 to be mixed and expeditiously dispensed to fillmultiple cavities 64.

In one alternative embodiment, the filling material is conveyed inalternating steps into the cavity portions of each respective vertebralbody prior to filling the next vertebral body. In this technique, theexpandable structure 56(1) is removed from the vertebral body, andfilling material is conveyed into the corresponding cavity portion 64A.The expandable structure 56(2) is then removed from the vertebral body,and filling material is conveyed into the corresponding cavity portion64B. If desired, the filling material can be allowed to harden to somedegree before the expandable structure 56(2) is removed from thevertebral body. The process is then repeated for each remainingvertebral body to be treated. In this embodiment, the vertebral body isdesirably substantially supported by the filling material and/or anexpandable structure during the filling process, which reduces and/oreliminates the opportunity for the cavity to collapse and/or corticalbone to displace in an undesired direction during the filling operation.

III. Instruments for Establishing Bilateral Access.

During a typical bilateral procedure, a patient lies on an operatingtable. The patient can lie face down on the table, or on either side, orat an oblique angle, depending upon the physician's preference.

A. Establishing Multiple Accesses

1. Use of Hand Held Instruments

For each access (see FIG. 16A), the physician introduces a spinal needleassembly 70 into soft tissue ST in the patient's back. Under radiologicor CT monitoring, the physician advances the spinal needle assembly 70through soft tissue down to and into the targeted vertebral body 26. Thephysician can also employ stereotactic instrumentation to guideadvancement of the spinal needle assembly 70 and subsequent tools duringthe procedure. In this arrangement, the reference probe for stereotacticguidance can be inserted through soft tissue and implanted on thesurface of the targeted vertebral body. The entire procedure can also bemonitored using tools and tags made of non-ferrous materials, e.g.,plastic or fiber composites, such as those disclosed in U.S. Pat. Nos.5,782,764 and 5,744,958, which are each incorporated herein byreference, which would be suitable for use in a computer enhanced,whole-room MRI environment.

The physician will typically administer a local anesthetic, for example,lidocaine, through the assembly 70. In some cases, the physician mayprefer other forms of anesthesia.

The physician directs the spinal needle assembly 70 to penetrate thecortical bone 28 and the cancellous bone 32 through the side of thevertebral body 26. Preferably the depth of penetration is about 60% to95% of the vertebral body 26.

The physician holds the stylus 72 and withdraws the stylet 74 of thespinal needle assembly 70. As FIG. 16B shows, the physician then slidesa guide pin instrument 76 through the stylus 72 and into the cancellousbone 32. The physician now removes the stylus 72, leaving the guide pininstrument 76 deployed within the cancellous bone 32.

The physician next slides an obturator instrument 78 over the guide pininstrument 76, distal end first, as FIG. 16C shows. The physician cancouple the obturator instrument 78 to a handle 80, which facilitatesmanipulation of the instrument 78.

The physician makes a small incision in the patient's back. Thephysician twists the handle 80 while applying longitudinal force to thehandle 80. In response, the obturator instrument 78 rotates andpenetrates soft tissue through the incision. The physician may alsogently tap the handle 80, or otherwise apply appropriate additionallongitudinal force to the handle 80, to advance the obturator instrument78 through the soft tissue along the guide pin instrument 76 down to thecortical bone entry site. The physician can also tap the handle 80 withan appropriate striking tool to advance the obturator instrument 78 intoa side of the vertebral body 26 to secure its position.

The obturator instrument 78 shown in FIG. 16C has an outside diameterthat is generally well suited for establishing a lateral access.However, if access is desired through the more narrow region of thevertebral body 26, e.g., a pedicle 42 (called transpedicular access),the outside diameter of the obturator instrument 78 can be reduced (asFIG. 17 shows). The reduced diameter of the obturator instrument 78 inFIG. 17 mediates against damage or breakage of the pedicle 42. Thereduced diameter obturator instrument 78 shown in FIG. 17 includes apointed tip 82 to help secure its position against cortical bone 28. Itshould be understood that the disclosed methods and devices are wellsuited for use in conjunction with other approach paths, such aspedicular, extra-pedicular, posterolateral and anterior approaches, withvarying results.

The physician then proceeds to slide the handle 80 off the obturatorinstrument 78 and to slide a cannula instrument 84 over the guide pininstrument 76 and, further, over the obturator instrument 78. Ifdesired, the physician can also couple the handle 80 to the cannulainstrument 84, to apply appropriate twisting and longitudinal forces torotate and advance the cannula instrument 84 through soft tissue ST overthe obturator instrument 78. When the cannula instrument 84 contactscortical bone 28, the physician can appropriately tap the handle 80 witha striking tool to advance the end surface into the side of thevertebral body 26 to secure its position.

When a reduced diameter obturator 78 is used, as shown in FIG. 17, thecannula instrument 84 can carry a removable inner sleeve 86 (as FIG. 17also shows) to center the cannula instrument 84 about the reduceddiameter obturator instrument 78 during passage of the cannulainstrument 84 to the treatment site.

The physician now withdraws the obturator instrument 78, sliding it offthe guide pin instrument 76, leaving the guide pin instrument 76 and thecannula instrument 84 in place. When a reduced diameter obturatorinstrument 78 is used, the physician can remove the inner centeringsleeve 86.

As FIG. 16D shows, the physician slides a drill bit instrument 88 overthe guide pin instrument 76, distal end first, through the cannulainstrument 84, until contact between the machined or cutting edge 90 ofthe drill bit instrument 88 and cortical bone 28 occurs. The physicianthen couples the drill bit instrument 88 to the handle 80

Guided by X-ray (or another external visualizing system), the physicianapplies appropriate twisting and longitudinal forces to the handle 80,to rotate and advance the machined edge 90 of the drill bit instrument88 to open a lateral passage PLA through the cortical bone 28 and intothe cancellous bone 32. The drilled passage PLA preferably extends nomore than 95% across the vertebral body 26.

As FIG. 18A shows, the drill bit instrument 88 can include a flexibleshaft portion 92 to aid in its manipulation. The flexible shaft portion92 allows the cutting edge 90 of the instrument 88 to flex relative tothe axis of the instrument. As FIG. 18A also shows, the cannulainstrument 84 can, if desired, include a deflector element 94 on itsdistal extremity, to flex the flexible shaft portion 92 and guide thecutting edge 90 along a desired drill axis. Desirably, in such aflexible embodiment the drill bit instrument 88 is made of a flexibleplastic material, e.g., polyurethane, or a flexible metal materialencapsulated in or surrounding a plastic material, to possess sufficienttorsional rigidity to transmit rotating cutting force to bone.

Alternatively, as FIG. 18B shows, the drill bit instrument 88 caninclude an interior lumen 180 to accommodate passage of a guide wire182. In this arrangement, the flexible shaft portion 92 conforms to thepath presented by the guide wire 182. The guide wire 182, for example,can be pre-bent, to alter the path of the cutting edge 90 after itenters the vertebral body. Alternatively, the guide wire can be made ofmemory wire, shape memory alloys (including nickel-titanium, copper oriron based alloys, to name a few), or comprise a self-steering guidingcatheter.

Still alternatively, as FIG. 18C shows, the drill bit instrument 88itself can carry interior steering wires 184. The steering wires 184 areoperated by the physician using an external actuator 186, to deflect theflexible shaft portion 92, and with it the cutting edge, without aid ofa guide wire and/or cannula instrument 84.

Further details regarding the formation of cavities within cancellousbone, which are not symmetric with relation to the axis of a vertebralbody, can be found in U.S. Pat. No. 5,972,015, entitled “ExpandableAsymmetric Structures for Deployment in Interior Body Regions,” which isincorporated herein by reference.

Once the passage PLA in cancellous bone 32 has been formed, thephysician removes the drill bit instrument 88 and the guide pininstrument 76, leaving only the cannula instrument 84 in place, as FIG.16E shows. The passage PLA made by the drill bit instrument 88 remains.Subcutaneous lateral access to the cancellous bone 32 has beenaccomplished.

The physician repeats the above described sequence of steps, asnecessary, to form each access desired. In FIG. 13, six accesses aremade.

2. Using Composite Hand Held Instruments

Other forms of hand held instruments may be used to provide access.

For example, FIGS. 27 and 28 show a composite instrument 310 that can beused for this purpose. The composite instrument 310 includes a trocarinstrument 320 and a cannula instrument 340. The composite instrument310 also includes a composite handle 312 comprising a first handle 322and a second handle 342. The composite handle 312 aids a physician inmanipulating the composite instrument 310. Still, as FIGS. 29A and 29Bshow, a physician can also desirably use the first handle 322 toindependently manipulate the trocar instrument 320 or the second handle342 to independently manipulate the cannula instrument 340 during use.

The trocar instrument 320 comprises a trocar 330 having a distal endthat is tapered to present a penetrating surface 334. In use, thepenetrating surface 334 is intended to penetrate soft tissue and/or bonein response to pushing and/or twisting forces applied by the physicianat the first handle 322, or the composite handle 312.

The cannula instrument 340 performs the function of the cannulainstrument 84 previously described, but also includes the handle 342,which mates with the handle 322 to form the composite handle 312. Inthis embodiment, the cannula instrument 84 is desirably somewhat largerin diameter than and not as long as the trocar 330. The cannulainstrument 84 includes an interior lumen 344 that is sized to accept thetrocar 330. The size of the interior lumen 344 desirably allows thecannula instrument 84 to slide and/or rotate relative to the trocar 330,and vice versa. The distal end 354 of the cannula instrument 84 presentsan end surface 360 that desirably presents a low-profile surface, whichcan penetrate soft tissue surrounding the trocar 330 in response topushing and/or twisting forces applied at the composite handle 312 orthe second handle 342.

In use, as shown in FIG. 30, the physician directs the compositeinstrument 310 such that the trocar 330 and the cannula instrument 84penetrate the cortical bone and the cancellous bone of the targetedvertebra. If desired, the physician can twist the composite handle 312while applying longitudinal force to the handle 312. In response, thepenetrating end surface 334 of the trocar 330, and the end surface ofthe cannula instrument 84 rotate and penetrate soft tissue and/or bone.

If penetration through the cortical bone and into the cancellous bone isnot achievable by manual advancement of the composite instrument 310, aphysician can continue penetration by gently striking a striking plate314 on the composite handle 312 with a blunt instrument such as asurgical hammer (not shown), or otherwise applying appropriateadditional longitudinal force to the composite handle 312, to advancethe distal end 334 of the trocar 330 and the end surface of the cannulainstrument 84.

If desired, the physician can utilize a spinal needle assembly 70, asalready described, to initially access the vertebral body. In thisarrangement, the composite instrument 310 is later guided through softtissue and into the targeted vertebra body along the stylet 74, which(in this arrangement) passes through an interior lumen in the trocar 330(not shown) Once the trocar 330 has sufficiently penetrated corticalbone, the physician can withdraw the stylet 74, thereby arriving at thestep in the procedure shown in FIG. 30.

After penetrating the cortical bone, the physician may continueadvancing the composite instrument 310 through the cancellous bone ofthe vertebral body to form the passage through the cancellous bone, asalready described. The trocar 330 may then be withdrawn from the cannulainstrument 84. The cannula instrument 84 remains to provide access tothe passage formed in the interior of the vertebral body, in the mannerpreviously described.

Alternatively, after penetrating the cortical bone, the physician maychoose to withdraw the trocar 330 from the cannula 50 and form thepassage in the cancellous bone using a drill bit instrument 88, as FIG.31 shows. In such a case, the physician removes the trocar 330 and, inits place, advances the drill bit instrument 88 through the cannulainstrument 84, as FIG. 31 shows.

With the removal of the drill bit instrument 88, access to thecancellous bone has been accomplished.

Further details about the structure and use of the composite instrument310 are found in copending U.S. patent application Ser. No. 09/421,635,filed Oct. 19, 1999, and entitled “Hand-Held Instruments that AccessInterior Body Regions,” which is incorporated herein by reference.

3. Breach Prevention and Plugging

To create access into the vertebral body in the manners shown in FIGS.16A to 16D, the physician typically advances a stylet 74 of the spinalneedle assembly 70 and also the cutting edge of the drill bit instrument88 a significant distance into the cancellous bone 32, as FIGS. 16B and16D show, toward cortical bone 28 on the anterior wall of the vertebralbody 26. The density of the cancellous bone 32 desirably offersresistance to the passage of these instruments, to thereby providetactile feed back to the physician, which aids in guiding theirdeployment. Still, the density of cancellous bone 32 is not uniform andcan change abruptly. Even with the utmost of care and skill, it ispossible that the stylet 74 or the cutting edge 90 can slide into andpoke through cortical bone 28 in the anterior wall of the vertebral body26. This can create a hole or breach B in the anterior cortical wall 28of the vertebral body 26, as FIG. 19 shows.

To aid in the advancement of the cutting edge 90 through cancellous bone32 (see FIG. 20A), the drill bit instrument 88 may include a mechanicalstop 96. In use, the mechanical stop 96 abuts against the proximal endof the cannula instrument 84. The abutment stops further advancement ofthe drill bit instrument 88 into the interior of the vertebral body 26.

The location of the mechanical stop 96 may be adjustable, to providevariable lengths of advancement, depending upon the size of thevertebral body 26 or other bone volume targeted for treatment.

Alternatively, or in combination, the drill bit instrument 88 mayinclude markings 98 located along its length at increments from itsterminus. The markings 98 register with the exposed proximal edge of thecannula instrument 84 (see FIG. 20A), to allow the physician to remotelygauge the position of the instrument in the vertebral body 26.

To aid the advancement of the stylet 74, the trocar 330, or the drillbit instrument 88 within the vertebral body, without breach of theanterior cortical wall, the physician can also make use of a corticalwall probe 140, as shown in FIG. 20B. The cortical wall probe 140comprises a generally rigid stylet body 142 having a blunt distal tip144, which desirably cannot easily pierce the anterior cortical wall ofthe vertebral body. In the illustrated embodiment, the blunt distal tip144 comprises a rounded ball shape.

The cortical wall probe 140 can be deployed through the formed accessopening before any significant penetration of cancellous bone occurs.For example, after the access opening is formed using the spinal needleassembly 70, but before the stylus 72 and stylet 74 are advanced asignificant distance into cancellous bone, the stylet 74 can bewithdrawn and, instead, the cortical wall probe 140 advanced through thestylus 72. The physician advances the cortical wall probe 140 throughcancellous bone, until the physician tactilely senses contact betweenthe blunt distal tip 144 and the anterior. cortical wall. Desirably, theprobe 140 is radiopaque, so that its advancement through cancellous boneand its contact with the anterior cortical wall within the vertebralbody can be visualized, e.g., either by x-ray or real time fluoroscopyor MRI. Using the cortical wall probe 140, the physician can gauge thedistance between the access opening into the vertebral body and theanterior cortical wall, in a manner that avoids penetration of theanterior cortical wall.

The cortical wall probe 140 can carry length markings 146 on itsproximal region, which, when contact with the anterior cortical walloccurs and/or is imminent, indicate the distance a subsequent instrumentcan be advanced down the stylus 72 (or cannula instrument 84) beforecontacting the anterior cortical wall. The information obtained from thecortical wall probe 140 can also be used to set the mechanical stop 96(previously described), to physically prevent advancement of the trocar330 or drill bit instrument 88 before contact with the anterior corticalwall occurs.

In the event of a breach or suspected breach of the anterior corticalwall of the vertebral body, the physician can alternatively utilize thecortical wall probe 140 to safely and easily determine the existenceand/or extent of a wall breach. Because the distal tip 144 of the probeis blunt, the tip 144 desirably will not easily pass through an intactanterior cortical wall, which allows the physician to “tap” the toolalong the inner surface of the anterior cortical wall while searchingfor breaches. Where a wall breach has occurred, and the tool could passthrough the breach, the blunt tip 144 of the tool desirably will notpierce or damage soft tissues, such as the aorta or major veins, locatedforward of the cortical wall. If desired, the blunt tip 144 canalternatively be formed of a soft, deformable material such as rubber orplastic.

If a breach B occurs, a suitable material may be placed into the breachB to plug it. For example, a demineralized bone matrix material, such asGRAFTON™ material, may be used. The material can be placed, e.g., on thedistal end of the obturator instrument 78 or trocar 330. The instrument78 is deployed carrying the plugging material to the exterior side wallwhere the breach B occurs. The instrument 78 deposits the pluggingmaterial in the breach B, to thereby close it from the outside of thevertebral body 26.

The physician can take steps to counteract undetermined cortical wallbreaches, either as may possibly preexist before cavity formation orwhich may possibly exist after cavity formation. Even if a breach is notknown to exist, the physician can nevertheless elect to insert asuitable plug material (e.g., GRAFTON™ bone matrix material, orCollagraft™ sheet material, or a mesh-type material) into the vertebralbody, either before or after the structure 56 is expanded. The presenceof a plug material guards against the possibility of leaks, whether theyexist or not. Furthermore, if inserted before the structure 56 isexpanded, the presence of the plug material in the vertebral body canserve to make the distribution of the expansion force of the structure56 more uniform. The presence of the plug material within the vertebralbody as the structure 56 expands can also protect against protrusion ofthe expanding structure 56 through any preexisting breach in thecortical wall as well as any breaches created during expansion of thestructure 56, or can otherwise protect weakened cortical walls duringexpansion of the structure 56.

4. Cannula Locking Device

Referring to FIG. 26A, a cannula locking device 190 can be used to aidin stabilizing the cannula instrument 84 while accessing a vertebralbody. The locking device 190 can be variously constructed.

In the embodiment shown in FIG. 26A, the locking device 190 includes agenerally planar base 192. In use, the base 192 rests upon a skinsurface surrounding the targeted incision site. If desired, the base 192can incorporate an adhesive (not shown) to secure the base to thepatient's skin or to other material located at or near the surgicalsite.

An instrument grip 194 is supported on the base 192. The instrument grip194 includes a channel 218 which slidingly receives the cannulainstrument 84, which, in this embodiment, is intended to be placed intothe grip 194 distal end first. A ring 220, threaded to the grip 194, canbe provided to tighten the channel 218 about the cannula instrument 84,to thereby prevent axial movement of the cannula instrument 84 withinthe channel 218.

The grip 194 also includes a tenon 196, which fits within a mortise 198on the base 192. The mortise 198 and tenon 196 together form a joint200. The grip 194 pivots 360-degrees in transverse and/or orbital pathswithin the joint 200.

The mortise 198 is bounded by a collet 210, about which a retaining ring202 is threadably engaged. Twisting the ring 202 in one direction (e.g.,clockwise) closes the collet 210 about the tenon 196, locking theposition of the grip 194 relative to the base 192. Twisting the ring 202in an opposite direction opens the collet 210 about the tenon 196,freeing the grip 194 for pivotal movement relative to the base 192.

To use the device 190, the physician manipulates the cannula instrument84 held in the grip 194 into a desired axial and angular orientation.The physician thereafter locks the grip 194 (tightening the rings 202and 220) to hold the cannula instrument 84 in the desired axial andangular orientation. The physician can manipulate and lock the cannulainstrument 84 in any desired order, either before or after passage ofthe instrument 84 through the skin, and/or before or after passage ofthe instrument 84 through cortical bone, or combinations thereof.Markings 204 on the grip 194 and base 192 allow the physician to gaugemovement of the grip 194 relative to the base 192 or another referencepoint.

The locking device 190 is preferably made from a material that is nothighly radiopaque, e.g., polyurethane or polycarbonate. The device 190will therefore not obstruct fluoroscopic or x-ray visualization of thecannula instrument 84 during use.

When locked, the device 190 prevents unintended movement of the cannulainstrument 84 along the skin surface. The likelihood that the cannulainstrument 84 will be bent or its position inadvertently shifted duringuse is thereby mitigated. The device 190 also allows the physician toremove his/her hands from the instrument 84, e.g., to allow clearfluoroscopy or x-ray visualization. The device 190 obviates the need forother types of clamps that are radiopaque or are otherwise not wellsuited to the task.

As FIG. 26B shows, in an alternative embodiment, the retaining ring 202can be loosened to a point that opens the collet 210 enough to free thegrip 194 from the base 192. In this arrangement, the grip 194 comprisesmembers 206 and 208 that can be split apart when separated from theconfines of the collet 210. The cannula instrument 84 can be capturedbetween the spit-apart members 206 and 208 as they are fitted backtogether, obviating the need to load the cannula instrument 84 distalend first in the grip 194.

When fitted together, the tenon 196 can be returned to the mortise 198.The retaining ring 202 can be tightened sufficiently to close the collet210 about the tenon 196, forming the joint 200. Further tightening ofthe retaining ring 202 about the mortise 198 closes the joint 200 (asbefore described), locking the grip 194 a desired orientation relativeto the base 192. Subsequent loosening of the retaining ring 202 permitsseparation of the grip 194 from the base 192, so that the members 206and 208 can be split apart to free the cannula instrument 84. In oneembodiment, the grip 194 can contact the cannula directly, such that thecannula is substantially “locked ” in position when the grip 194 iscompressed against the cannula. In an alternate embodiment, an O-ring(not shown) can be located within the grip 194, such that compression ofthe grip causes the O-ring to push against the cannula, desirablysubstantially “locking” the cannula in position within the grip 194.

B. Forming the Cavities

Once the accesses PLA have been formed, the physician advancesindividual catheter tubes 50 through the cannula instrument 84 andpassage of each access, into the interior volume of the associatedvertebral body 26A, 26B, and 26C. FIG. 16F shows this deployment invertebral body 26A.

The expandable structures 56(1) to 56(6) are then expanded in thealternating, step wise fashion as already described. The compressionforms the interior cavity 64 in each vertebral body 26A, 26B, and 26C.

As FIGS. 4 and 5 show, the expandable structure 56 can carry at leastone radiopaque marker 102, to enable remote visualization of itsposition within the vertebral body 26. In the illustrated embodiment,the expandable structure 56 carries a radiopaque marker 102 on both itsdistal and proximal end.

As before described, when fluoroscopic or CT visualization is used tomonitor expansion of the structure 56, the fluid used to cause expansionof the structure 56 is preferably rendered radiopaque (e.g., usingRenografin™ material). The visualization instrument (e.g., a C-armfluoroscope) is typically positioned on the operating table to viewlaterally along one side of the spinal column. The presence ofradiopaque expansion medium in a expanded structure 56 in the vertebralbody 26 can block effective visualization elsewhere in the vertebralbody, e.g., where cavity formation using another structure 56 or wherevertebroplasty or another form of treatment is intended to occur.

Visualization can be facilitated under these circumstances by removal ordilution of the radiopaque medium within the structure 56 after thestructure is expanded to create a cavity.

In one embodiment (see FIG. 32), an exchange chamber 400 is provided,which is divided into two compartments 402 and 404 by a piston 414 thatis movable by pressure upon a plunger 420. Dual lumens 406 and 408communicate with the interior of the structure 56. The lumen 406communicates with the source 422 of radiopaque medium 410 to convey themedium 410 into the structure 56 to cause expansion and cavity formationin the first instance. The lumen 406 also communicates with thecompartment 402 on one side of the piston 414.

The other compartment 404 of the chamber 400 contains a replacementexpansion medium 412. The replacement medium 412 is free of a radiopaquematerial or, if desired, can contain a partially-radiopaque material.The lumen 408 communicates with this compartment 404.

After expansion of the structure 56 with the radiopaque medium 410,movement of the piston 414 will draw the radiopaque medium 410 from thestructure 56 (through lumen 402). Simultaneously, the piston 414 willdisplace the radiopaque-free medium 412 into the structure 56 (throughlumen 404). Piston movement exchanges the radiopaque medium 410 with theradiopaque-free medium 412, without collapsing the structure 56.

In an alternative embodiment, an ion exchange material for theradiopaque material in the medium 410 (e.g., iodine) can be introducedinto the radiopaque medium 410 contained within the structure 56. Theion exchange material selectively binds the radiopaque material,diluting the radiopaque qualities of the medium 410. The radiopaquemedium 410 can be circulated through an ionic exchange chamber outsidethe structure 56, or the ion exchange material can be introduced intothe structure 56 through an interior lumen within the structure 56itself.

Alternatively, a material that causes precipitation of radiopaquematerial can be introduced into the radiopaque medium 410 within thestructure 56 (e.g., through an interior lumen). The precipitationselectively causes the radiopaque material to settle downward within thestructure 56, out of the lateral visualization path, thereby dilutingthe radiopaque qualities of the medium 410.

As FIG. 5 shows, the expandable structure 56 can also include aninterior tube 104. The interior tube 104 contains an interior lumen 106that passes through the expandable structure 56.

The interior lumen 106 can be used to convey a flowable material orliquid, e.g. saline or sterile water, to flush materials free of thedistal region of the structure 56, when in use. The interior lumen 106can also be used to aspirate liquid material from the interior of thevertebral body 26 as the procedure is performed. The interior lumen 106can also be used to introduce a thrombogenic material, e.g., a clottingagent, into contact with cancellous bone 32 during the procedure. Theexpandable structure 56 itself can be also dipped into thrombin prior toits introduction into the vertebral body 26 to facilitate in situcoagulation.

The interior lumen 106 can also be sized to receive a stiffening memberor stylet 108 (see FIG. 5). The stylet 108 keeps the structure 56 in adesired distally straightened condition during its passage through thecannula instrument 84. Once the structure 56 is located in the desiredlocation within cancellous bone, the physician can remove the stylet108, and thereby open the interior lumen 106 for conveyance of liquidsto and from cancellous bone, as just described.

The stylet 108 can also have a preformed memory, to normally bend itsdistal region. The memory is overcome to straighten the stylet 108 whenpassed through the cannula instrument 84. However, as the structure 56and stylet 108 advance free of the cannula instrument 84, passing intocancellous bone 32, the preformed memory bends the stylet 108. The bentstylet 108 shifts the axis of the structure relative to the axis of theaccess path PLA. The prebent stylet 108, positioned within the interiorof the structure 56, aids in altering the geometry of the structure 56to achieve a desired orientation when deployed for use.

If the stylet 108 is comprised of a shape memory alloy, such asnickel-titanium(Nitinol), copper or iron based alloys, the distal end ofthe stylet 108 can be set to a prebent “parent shape,” and thensubsequently bent to a substantially straight shape for introductioninto the vertebral body. When the stylet 108 is in its desired position,and bending of the distal end is desired, heat can be applied to theproximal end of the stylet 108, which desirably will cause the distalend of the stylet 108 to assume its parent shape in a known manner.Alternatively, the stylet 108 can be comprised of a shape memoryallowing material having a transition temperature at or below human bodytemperature. Such a stylet 108 can be cooled prior to and/or duringintroduction into the human body, and once in the proper position, thecooling source can be removed, and the patient's body heat will causethe stylet 108 to assume its pre-bent parent shape. If desired, thestylet can be initially positioned within the vertebral body, with thedistal end deflecting within the cancellous bone, or the distal end canbe deflected during insertion into the vertebral body.

As FIG. 25 shows, the catheter tube 50 can itself carry a drill bitelement 170. The drill bit element 170 may be variously constructed. Asshown in FIG. 25, the drill bit element 170 comprises a metal cuttingcap bonded or otherwise mounted on the distal end of the interiorcatheter tube 104, beyond the expandable structure 56. In thisarrangement, the stylet 108 can include a keyed distal end 172, whichmates within an internal key way 174 in the drill bit element 170. Thestylet 108 thereby serves to stiffen the distal end of the catheter tube104, so that torsional and compressive loads can be applied to the drillbit element 170. Alternatively, the interior structure of the cathetertube 104 can be otherwise reinforced to transmit torsional andcompressive load forces to the drill bit element 170. Using the drillbit element 170, the physician can open an access opening in thecortical bone, without use of the separate drill bit instrument 88.

1. Desired Physical and Mechanical Properties for the ExpandableStructure

The material from which the structure 56 is made should possess variousphysical and mechanical properties to optimize its functionalcapabilities to compact cancellous bone. Important properties are theability to expand its volume; the ability to deform in a desired waywhen expanding and assume a desired shape inside bone; and the abilityto withstand abrasion, tearing, and puncture when in contact withcancellous bone.

2. Expansion Property

A first desired property for the structure material is the ability toexpand or otherwise increase its volume without failure. This propertyenables the structure 56 to be deployed in a collapsed, low profilecondition subcutaneously, e.g., through a cannula, into the targetedbone region. This property also enables the expansion of the structure56 inside the targeted bone region to press against and compresssurrounding cancellous bone, or move cortical bone to a prefracture orother desired condition, or both.

The desired expansion property for the structure material can becharacterized in one way by ultimate elongation properties, whichindicate the degree of expansion that the material can accommodate priorto failure. Sufficient ultimate elongation permits the structure 56 tocompact cortical bone, as well as lift contiguous cortical bone, ifnecessary, prior to wall failure. Desirably, the structure 56 willcomprise material able to undergo an ultimate elongation of at least50%, prior to wall failure. when expanded outside of bone. Moredesirably, the structure will comprise material able to undergo anultimate elongation of at least 150%, prior to wall failure, whenexpanded outside of bone. Most desirably, the structure will comprisematerial able to undergo an ultimate elongation of at least 300%, priorto wall failure, when expanded outside of bone.

Alternatively, the structure 56 can comprise one or more non-compliantor partially compliant materials having substantially lower ultimateelongation properties, including, but not limited to, kevlar, aluminum,nylon, polyethylene, polyethylene-terephthalate (PET) or mylar. Such astructure would desirably be initially formed to a desired shape andvolume, and then contracted to a collapsed, lower profile condition forintroduction through a cannula into the targeted bone region. Thestructure could then be expanded to the desired shape and volume topress against and compress surrounding cancellous bone and/or movecortical bone to a prefracture or desired condition, or both. As anotheralternative, the structure could comprise a combination ofnon-compliant, partially compliant and/or compliant materials.

3. Shape Property

A second desired property for the material of the structure 56, eitheralone or in combination with the other described properties, is theability to predictably deform during expansion, so that the structure 56consistently achieves a desired shape inside bone.

The shape of the structure 56, when expanded in bone, is desirablyselected by the physician, taking into account the morphology andgeometry of the site to be treated. The shape of the cancellous bone tobe compressed and/or cortical bone to be displaced, and the localstructures that could be harmed if bone were moved inappropriately, aregenerally understood by medical professionals using textbooks of humanskeletal anatomy along with their knowledge of the site and its diseaseor injury, and also taking into account the teachings of U.S. patentapplication Ser. No. 08/788,786, filed Jan. 23, 1997, and entitled“Improved Inflatable Device for Use in Surgical Protocol Relating toFixation of Bone,” which is incorporated herein by reference. Thephysician is also desirably able to select the desired expanded shapeinside bone based upon prior analysis of the morphology of the targetedbone using, for example, plain film x-ray, fluoroscopic x-ray, or MRI orCT scanning.

Where compression of cancellous bone and/or cavity creation is desired,the expanded shape inside bone is selected to optimize the formation ofa cavity that, when filled with a selected material, provides supportacross the region of the bone being treated. The selected expanded shapeis made by evaluation of the predicted deformation that will occur withincreased volume due to the shape and physiology of the targeted boneregion.

Where displacement of cortical bone is desired, the expanded shape canbe chosen to maximize the amount of force the structure exerts oncortical bone, maximize force distribution over the largest possiblesurface area of the cortical bone and/or maximize displacement of thecortical bone in one or more desired directions. Alternatively, thestructure can be designed to impart a maximum force on a specific areaof the cortical bone so as to cause desired fracture and/or maximumdisplacement of specific cortical bone regions.

To aid in selecting a suitable size for the expandable structure 56, thetrocar 330 of the composite instrument 310 (see FIGS. 27 and 28) cancarry an array of grooves or like markings 380, which can be viewedunder fluoroscopic visualization. The markings 380 allow the physicianto estimate the distance across the vertebral body, thereby making itpossible to estimate the desired size of the expandable structure 56.Because the cannula instrument 84 is a relatively. thin-walledstructure, and the trocar 330 is a relatively thicker solid structure,the physician is able to visualize the marking 380 by fluoroscopy, evenwhen the markings 380 are inside the cannula instrument 84.

In some instances, it is desirable, when creating a cavity, to also moveor displace the cortical bone to achieve the desired therapeutic result.Such movement is not per se harmful, as that term is used in thisSpecification, because it is indicated to achieve the desiredtherapeutic result. By definition, harm results when expansion of thestructure 56 results in a worsening of the overall condition of the boneand surrounding anatomic structures, for example, by injury tosurrounding tissue or causing a permanent adverse change in bonebiomechanics.

If desired, the structure 56 can be used to generate sufficient force tofracture cortical bone and position the fractured cortical bone in a neworientation and/or into a more desired position. Where the bone hasfractured and/or compressed in the past, and subsequently healed, thepresent methods and devices can be utilized to safely reposition thecortical bone to a more desired position. For example, where a vertebralcompression fracture has healed in a depressed and/or fracturedposition, the disclosed devices and methods can be utilized tore-fracture and reposition the fractured bone to a more desirableposition and/or orientation. By generating sufficient force to fracturethe bone from the interior, through expansion of an expandable body,only a single access portal through the cortical bone need be formed.

If desired, the structure could alternatively be used in conjunctionwith various devices, including but not limited to lasers, drills,chisels or sonic generators (e.g. lithotripers), these devices beingused to selectively weaken and/or fracture cortical bone along desiredlines and/or in a desired manner. Once the targeted cortical bone issufficiently weakened, the structure 56 can be used to fracture the boneand/or reposition the cortical bone to a new orientation and/or into amore desired position.

In a similar manner, the structure 56 can be used to fracture andreposition a portion of the cortical bone, such as where the bone hasgrown and/or healed in a deformed condition. For example, in a patienthaving severe scoliosis (e.g., osteopathic scoliosis), the vertebralcolumn may be laterally curved due to bone deformation. The presentmethods and devices can be utilized to safely fracture and/or repositionthe cortical bone to a more desired position. If desired, sections ofthe bone can be scored, weakened and/or pre-fractured by various devicesincluding, but not limited to, sharp knives, saws, awls, drills, lasersand/or lithotripters, creating desired lines along which the bone willtend to fracture. The depressed sections of the vertebral body candesirably be elevated and reinforced, thereby reducing the lateral curveof the vertebral column and preventing further lateral deformation ofthe spine. By fracturing and/or displacing only a portion of thecortical bone, the present methods and devices minimize unnecessarymuscular-skeletal trauma while permitting treatment of the disease.

As one general consideration, in cases where the bone disease causingfracture (or the risk of fracture) is the loss of cancellous bone mass(as in osteoporosis), the selection of the expanded shape of thestructure 56 inside bone should take into account the cancellous bonevolume which should be compacted to achieve the desired therapeuticresult. An exemplary range is about 30% to 90% of the cancellous bonevolume, but the range can vary depending upon the targeted bone region.Generally speaking, compacting less of the cancellous bone volume leavesmore uncompacted, diseased cancellous bone at the treatment site.

Another general guideline for the selection of the expanded shape of thestructure 56 inside bone is the amount that the targeted fractured boneregion has been displaced or depressed. The expansion of the structure56 inside a bone can elevate or push the fractured cortical wall back toor near its anatomic position occupied before fracture occurred. Wherethe structure 56 directly contacts the depressed cortical bone, andelevates the cortical bone through direct contact with the expandingstructure, compaction of cancellous bone may not be necessary ordesired.

For practical reasons, it is desired that the expanded shape of thestructure 56 inside bone, when in contact with cancellous bone,substantially conforms to the shape of the structure 56 outside bone,when in an open air environment. This allows the physician to select inan open air environment a structure having an expanded shape desired tomeet the targeted therapeutic result, with the confidence that theexpanded shape inside bone will be similar in important respects.

In some instances, it may not be necessary or desired for the structureto predictably deform and/or assume a desired shape during expansioninside bone. Rather, it may be preferred that the structure expand in asubstantially uncontrolled manner, rather than being constrained in itsexpansion. For example, where compaction of weaker sections of thecancellous bone is desired, it may be preferred that the structureinitially expand towards weaker areas within the bone. In such cases,the structure can be formed without the previously-described shapeand/or size, and the expanded shape and/or size of the structure can bepredominantly determined by the morphology and geometry of the treatedbone.

An optimal degree of shaping can be achieved by material selection andby special manufacturing techniques, e.g., thermoforming or blowmolding, as will be described in greater detail later.

4. Toughness Property

A third desired property for the structure 56, either alone or incombination with one or more of the other described properties, is theability to resist surface abrasion, tearing, and puncture when incontact with cancellous bone. This property can be characterized invarious ways.

One way of measuring a material's resistance to abrasion, tearing and/orpuncture is by a Taber Abrasion test. A Taber Abrasion test evaluatesthe resistance of a material to abrasive wear. For example, in a TaberAbrasion test configured with an H-18 abrasive wheel and a 1 kg load for1000 cycles (ASTM Test Method D 3489), Texin® 5270 material exhibits aTaber Abrasion value of approximately 75 mg loss. As another example,under the same conditions Texin® 5286 material exhibits a Taber Abrasionvalue of approximately 30 mg loss. Typically, a lower Taber Abrasionvalue indicates a greater resistance to abrasion. Desirably, oneembodiment of an expandable structure will comprise material having aTaber Abrasion value under these conditions of less than approximately200 mg loss. More desirably, the structure will comprise material havinga Taber Abrasion value under these conditions of less than approximately145 mg loss. Most desirably, the structure will comprise material havinga Taber Abrasion value under these conditions of less than approximately90 mg loss. Of course, materials having a Taber Abrasion value ofgreater than or equal to 200 mg loss may be utilized to accomplish someor all of the objectives of the present invention.

Another way of measuring a material's resistance to abrasion, tearingand/or puncture is by Elmendorf Tear Strength. For example, under ASTMTest Method D 624, Texin® 5270 material exhibits a Tear Strength of1,100 lb-ft/in. As another example, under the same conditions, Texin5286 exhibits a Tear Strength of 500 lb-ft/in. Typically, a higher TearStrength indicates a greater resistance to tearing. Desirably, analternative embodiment of an expandable structure will comprise materialhaving a Tear Strength under these conditions of at least approximately150 lb-ft/in. More desirably, the structure will comprise materialhaving a Tear Strength under these conditions of at least approximately220 lb-ft/in. Most desirably, the structure will comprise materialhaving a Tear Strength under these conditions of at least approximately280 lb-ft/in. of course, materials having a Tear Strength of less thanor equal to 150 lb-ft/in may be utilized to accomplish some or all ofthe objectives of the present invention.

Another way of measuring a material's resistance to abrasion, tearingand/or puncture is by Shore Hardness. For example, under ASTM TestMethod D 2240, Texin® 5270 material exhibits a Shore Hardness of 70D. Asanother example, under the same conditions, Texin® 5286 materialexhibits a Shore Hardness of 86A. Typically, a lower Shore Hardnessnumber on a given scale indicates a greater degree of elasticity,flexibility and ductility. Desirably, another alternative embodiment ofan expandable structure will comprise material having a Shore Hardnessunder these conditions of less than approximately 75D. More desirably,the structure will comprise material having a Shore Hardness under theseconditions of less than approximately 65D. Most desirably, the structurewill comprise material having a Shore Hardness under these conditions ofless than approximately 100A. Of course, materials having a ShoreHardness of greater than or equal to 75D may be utilized to accomplishsome or all of the objectives of the present invention.

It should also be noted that another alternative embodiment of aexpandable structure incorporating a plurality of materials, such aslayered materials and/or composites, may possess significant resistanceto surface abrasion, tearing and puncture. For example, a layeredexpandable structure incorporating an inner body formed of materialhaving a Taber Abrasion value of greater than 200 mg loss and an outerbody having a shore hardness of greater than 75D might possesssignificant resistance to surface abrasion, tearing and puncture.Similarly, other combinations of materials could possess the desiredtoughness to accomplish the desired goal of compressing cancellous boneand/or moving cortical bone prior to material failure.

5. Creating a Pre-Formed Structure

The expansion and shape properties just described can be enhanced andfurther optimized for compacting cancellous bone by selecting anelastomer material, which also possess the capability of being preformed(i.e., to acquire a desired shape by exposure, e.g., to heat andpressure), e.g., through the use of conventional thermoforming or blowmolding techniques. Candidate materials that meet this criteria includepolyurethane, silicone, thermoplastic rubber, nylon, and thermoplasticelastomer materials.

In the illustrated embodiment, TEXIN® 5286 polyurethane material isused. This material is commercially available from Bayer in pellet form.The pellets can be processed and extruded in a tubular shape. Thestructure 56 can be formed by exposing a cut length of the tubularextrusion to heat and then enclosing the heated tube within a mold whilepositive interior pressure is applied to the tube length 60, such as ina conventional balloon forming machine.

Further details regarding the creation of the expandable structure 56can be found in copending U.S. patent application Ser. No. 09/420,529,filed Oct. 19, 1999, and entitled “Expandable Preformed Structures ForDeployment in Interior Body Regions”, which is incorporated herein byreference.

6. Saline Infusion

In the treatment of crush, compression, or depression fracture, theexpandable structure 56 serves to move cortical bone 28 back to itsoriginal or proper anatomic condition. This result can be achieved asthe cavity is formed, by expansion of the structure 56 within cancellousbone 32 to physically move surrounding compressed or depressed corticalbone 28. Alternatively, as previously described, the cortical bone canbe displaced through direct contact with the expanding structure.

It has been discovered that a localized vacuum condition may be createdwithin the cavity 64 in response to the deflation and removal of thestructure 56. The vacuum may abruptly move surrounding cortical bone 28,causing pain. The movement of bone after formation of the cavity 64 canalso take back some of the distance the cortical bone 28 has beendisplaced as a result of expanding the structure 56 to form the cavity64 in the first place. In a vertebral body 26, the vacuum can preventfull restoration of the vertebral body height.

As FIG. 21 shows, to prevent formation of the vacuum, a flowablematerial or sterile liquid 110, e.g., saline or radiopaque contrastmedium, can be introduced into the cavity 64 before and during deflationof the structure 56 and its removal from the cavity 64. The volume ofliquid 110 introduced into the cavity 64 at this time is not critical,except that it should be sufficient to prevent the formation of asignificant vacuum. For example, a volume of saline equal to or greaterthan the volume of the cavity will typically prevent significant vacuumformation. Alternatively, volumes of saline less than the volume of thecavity can also prevent significant vacuum formation to varying degrees.

The liquid 110 can be introduced through the interior lumen 106 passingthrough the structure 56, as previously described. Alternatively, asmall exterior tube can be carried along the catheter tube 50 orinserted separately through the cannula instrument 84 to conveyvacuum-preventing liquid 110 into the cavity 64.

Alternatively, air can be used to prevent vacuum formation. Oncepressure used to expand the structure 56 is released, air can passthrough the interior lumen 106 to replace the volume occupied by thecollapsing structure 56. If the rate of air flow through the interiorlumen 106 under ambient pressure is not sufficient to replace the volumeas it is formed, the air flow rate can be augmented by use of a pump.

C. Filling the Cavities

Upon formation of the cavities 64 (see FIG. 16G), the physician fills asyringe 112 with the desired volume of filling material 62, a batch ofwhich has been previously prepared. When using an expandable structure56 having a preformed configuration, the cavity volume created is known.The physician thereby knows the desired volume of material 62 to placein the syringe 112 for each cavity portion 64A and 64B formed in thevertebral body 26.

The physician attaches a nozzle 114 to the filled syringe 112. Thephysician then proceeds to deflate and remove the expandable structures56(1) to 56(6) through the associated cannula instrument 84, in thesequential fashion already described, and to fill the associated cavityportion 64A/64B with the material 62.

To fill a given cavity portion 64A/64B (see FIG. 16H), the physicianinserts the nozzle 114 through the associated cannula instrument aselected distance into the cavity portion, guided, e.g., by exteriormarkings 116 or by real-time fluoroscope or x-ray or MRI visualization.The physician operates the syringe 112 to cause the material 62 to flowthrough and out of the nozzle 114 and into the cavity portion. As FIG.16H shows, the nozzle 114 may posses a uniform interior diameter, sizedto present a distal end dimension that facilitates insertion into thevertebral body. To reduce the overall flow resistance, however, thenozzle 114 can possess an interior diameter (e.g., see FIG. 22A) thatsteps down from a larger diameter at its proximal region 118 to asmaller diameter near its distal end 120. This reduces the averageinterior diameter of the nozzle 114 to thereby reduce the overall flowresistance. Reduced flow resistance permits more viscous material to beconveyed into the vertebral body. The more viscous material isdesirable, because it has less tendency to exude from the bone. comparedto less viscous materials. In addition to the embodiment shown in FIG.22A, various other constructions are possible to create a reduceddiameter nozzle or tool for introducing material into bone. For example,as shown in FIG. 22B, a tool 160 can possess an interior lumen 162 thatgradually tapers from a larger interior diameter to a smaller interiordiameter. Or, as shown in FIG. 22C, a tool 164 can possess an interiorlumen 166 that steps from a larger to a smaller interior diameter. Anassociated cannula instrument 168 (see FIG. 22C) may also include areduced diameter passage, which is downsized to accommodate the reduceddiameter tool and to present less flow resistance to filling materialconveyed through the cannula instrument.

The reduced diameter tool may also be used in association with avertebroplasty procedure, which injects cement under pressure into avertebral body, without prior formation of a cavity, as will bedescribed later.

The filling material 62 may contain a predetermined amount of aradiopaque material, e.g., barium or tungsten, sufficient to enablevisualization of the flow of material 62 into the cavity portion. Theamount of radiopaque material (by weight) is desirably at least 10%,more desirably at least 20%, and most desirably at least 30%. Thephysician can thereby visualize the cavity filling process.

As material 62 fills the cavity portion, the physician withdraws thenozzle 114 from the cavity portion and into the cannula instrument 84.The cannula instrument 84 channels the material flow toward the cavityportion. The material flows in a stream into the cavity portion.

As FIG. 16H shows, a gasket 122 may be provided about the cannulainstrument 84 to seal about the access passage PLA. The gasket 122serves to prevent leakage of the material about the cannula instrument84.

The physician operates the syringe 112 to expel the material 62 throughthe nozzle 114, first into the cavity portion and then into the cannulainstrument 84. Typically, at the end of the syringe injection process,material 62 should extend from the cavity and occupy about 40% to 50% ofthe cannula instrument 84. Alternatively, the physician can utilize thesyringe 112 to fill the lumen of the nozzle 114 and/or cannulainstrument 84 with material 62, and then utilize a tamping instrument124 to expel the material from the lumen into the vertebral body.

When a desired volume of material 62 is expelled from the syringe 112,the physician withdraws the nozzle 114 from the cannula instrument 84.The physician may first rotate the syringe 112 and nozzle 114, to breakloose the material 62 in the nozzle 114 from the ejected bolus ofmaterial 62 occupying the cannula instrument 84.

As FIG. 16I shows, the physician next advances a tamping instrument 124through the cannula instrument 84. The distal end of the tampinginstrument 124 contacts the residual volume of material 62 in thecannula instrument 84. Advancement of the tamping instrument 124displaces progressively more of the residual material 62 from thecannula instrument 84, forcing it into the cavity portion. The flow ofmaterial 62 into the cavity portion, propelled by the advancement of thetamping instrument 124 in the cannula instrument 84, serves to uniformlydistribute and compact the material 62 inside the cavity portion, intoother cavities and/or openings within the bone, and into fracture lines,without the application of extremely high pressure.

The use of the syringe 112, nozzle 114, and the tamping instrument 124allows the physician to exert precise control when filling the cavityportion with material 62. The physician can immediately adjust thevolume and rate of delivery according to the particular localphysiological conditions encountered. The application of low pressure,which is uniformly applied by the syringe 112 and the tamping instrument124, allows the physician to respond to fill volume and flow resistanceconditions in a virtually instantaneous fashion. The chance ofoverfilling and leakage of material 62 outside the cavity portion issignificantly reduced.

Moreover, the tamping instrument 124 will desirably permithighly-controlled injection of material 62 under higher injectionpressures as well. For example, FIG. 32 depicts a material injectioninstrument 500 comprising a reduced diameter nozzle 180 and a stylet182. The stylet 182 is desirably sized to pass through the reduceddiameter nozzle 180. In turn, the nozzle 180 is desirably sized to passthrough the cannula instrument 184. For material strength, the nozzle180 can be formed from a substantially rigid metal material, e.g.,stainless steel or a high strength plastic.

The stylet 182 includes a handle 192, which rests on the proximalconnector 186 of the nozzle when the stylet 182 is fully inserted intothe nozzle 180. When the handle is rested, the distal ends of the stylet182 and nozzle 180 align. The presence of the stylet 182 inside thenozzle 180 desirably closes the interior bore.

In use, the nozzle 180 can be coupled to the syringe 104 and insertedthrough the cannula instrument 184 into a material-receiving cavity (notshown) formed within a bone. Material 62 in the syringe 104 is injectedinto the nozzle 180 where it desirably passes into the bone. When asufficient amount of material 62 is injected into the bone and/or nozzle180, the syringe 104 may be removed from the nozzle 180.

The stylet 182 can then be inserted into the nozzle 180, and advancedthrough the nozzle, desirably pressurizing the material 62 and pushingit out of the nozzle 180. In one disclosed embodiment, the stylet 182has a diameter of approximately 0.118 in. The cross-sectional area ofthis stylet 182 is approximately 0.010936 in², and the nozzle 180desirably contains approximately 1.5 cc of filler material. In thisembodiment, pushing the stylet 182 into the nozzle 180 with a force offorce of ten (10) pounds can produce a pressure of approximately 914lb-in² in the filler material 62 within the nozzle 180. In an alternateembodiment, the stylet 182 has a diameter of approximately 0.136 in. Aforce of ten (10) pounds utilized on this stylet can produce a pressureof approximately 688 lb-in² in the filler material 62 within the nozzle180.

The nozzle 180 and stylet 182 can be used in a similar manner as acombination ram 183 to push the filler material 62 through the cannulainstrument 184 into the bone. For example, where filler material 62 iswithin the cannula instrument 184, the insertion of the ram 183 into thecannula 184 will desirably displace the material 62, forcing thematerial 62 from the distal end of the cannula 184 into the bone. In oneembodiment, the diameter of the ram 183 is approximately 0.143 in. Inthis embodiment, pushing the ram 183 with a force of ten (10) pounds iscapable of producing a pressure of 622 lb-in² in the filler material 62within the cannula 184. As the ram 183 advances through the cannula 184,it will desirably displace the filler material 62 in the cannula 184.The ram 183, therefore, acts as a positive displacement “piston” or“pump,” which permits the physician to accurately gauge the preciseamount of filler material 62 that is injected into the bone.

If the filler material is very viscous, this material will typicallystrongly resist being pumped through a delivery system. Generally, thegreater distance the filler material must travel through the system, thegreater the pressure losses will be from such factors as viscosity ofthe material and frictional losses with the walls. In order to accountfor these losses, existing delivery systems typically highly pressurizethe filler material, often to many thousands of pounds of pressure. Notonly does this require stronger pumps and reinforced fittings for thedelivery system, but such systems often cannot dispense filler materialin very precise amounts. Moreover, if the filler material hardens overtime, the system must produce even greater pressures to overcome theincreased flow resistance of the material.

The disclosed systems and methods obviate and/or reduce the need forcomplex, high pressure injection systems for delivery of fillermaterials. Because the disclosed ram 183 travels subcutaneously throughthe cannula 184, and displaces filler material 62 out the distal end ofthe cannula 184, the amount of filler material being pushed by the ram183 (and the total amount of filler material 62 within the cannula 184)progressively decreases as filler material is injected into the bone.This desirably results in an overall decrease in resistance to movementof the ram during injection. Moreover, because the amount of materialbeing “pushed” by the ram 183 decreases, an increase in the flowresistance of the curing filler material does not necessarily require anincrease in injection pressure. In addition, because the ram 183 travelswithin the cannula 184, and can travel percutaneously to the injectionsite, the filler material need only be “pumped” a short length before itexits the cannula and enters the bone, further reducing the need forextremely high pressures. If injection of additional filler material isrequired, the ram can be withdrawn from the cannula, additional fillermaterial can be introduced into the cannula, and the process repeated.Thus, the present arrangement facilitates injection of even extremelyviscous materials under well controlled conditions. Moreover, byutilizing varying diameters of cannulas, nozzles and stylets in thismanner, a wide range of pressures can be generated in the fillermaterial 62. If desired, the disclosed devices could similarly be usedto inject filler material through a spinal needle assembly directly intobone, in a vertebroplasty-like procedure, or can be used to fill acavity created within the bone.

If desired, after the physician has filled the cavity with material 62,the physician may choose to continue injecting additional material 62into the vertebral body. Depending upon the local conditions within thebone, this additional material may merely increase the volume of thecavity (by further compacting cancellous bone), or may travel into thecompressed and/or uncompressed cancellous bone surrounding the cavity,which may serve to further compress cancellous bone and/or furtherenhance the compressive strength of the vertebral body.

When the physician is satisfied that the material 62 has been amplydistributed inside the cavity portion, the physician withdraws thetamping instrument 124 from the cannula instrument 84. The physicianpreferably first twists the tamping instrument 124 to cleanly breakcontact with the material 62.

Once all cavity portions have been filled and tamped in the abovedescribed manner, the cannula instruments 84 can be withdrawn and theincision sites sutured closed. The bilateral bone treatment procedure isconcluded.

Eventually the material 62, if cement, will harden to a rigid statewithin the cavities 64. The capability of the vertebral bodies 26A, 26B,and 26C to withstand loads has thereby been improved.

FIGS. 9B through 9D depict an alternate method of filling a cavity 60formed within a vertebral body. In this embodiment, a cannula instrument84 has been advanced through a pedicle 42 of the vertebral body by,providing access to a cavity 60 formed therein. A nozzle 180 is advancedinto the vertebral body, with the distal tip of the nozzle 180 desirablypositioned near the anterior side of the cavity 60. Filler material 62is slowly injected through the nozzle 180 into the cavity 60. Asinjection of filler material 62 continues, the nozzle 180 is withdrawntowards the center of the cavity 60. See FIG. 9c. Desirably, as thenozzle 180 is withdrawn, the distal tip of the nozzle 180 will remainsubstantially in contact with the growing bolus of filler material 62.Once the nozzle 180 is positioned near the center of the cavity 60,additional filler material 62 is injected through the nozzle 180 tosubstantially fill the cavity 60. The nozzle is then removed from thecavity 60.

If desired, the nozzle can be attached to a syringe 112 (see FIG. 33)containing filler material. In one embodiment, the syringe 112 willcontain an amount of filler material equal to the volume of the cavity60 formed within the vertebral body, with the nozzle containing anadditional 1.5 cc of filler material. In this embodiment, the cavity 60will initially be filled with filler material expelled from the syringe112. Once exhausted, the syringe 112 can be removed from the nozzle 180,a stylet 182 inserted into the nozzle 180, and the remaining fillermaterial within the nozzle 180 pushed by the stylet 182 into thevertebral body. Desirably, the additional filler material from thenozzle 180 will extravazate into the cancellous bone, compressadditional cancellous bone and/or slightly increase the size of thecavity 60.

The disclosed method desirably ensures that the cavity is completelyfilled with filler material. Because the patient is often positionedfront side (anterior side) down during the disclosed procedures, theanterior section of the cavity is often the lowest point of the cavity.By initially filling the anterior section of the cavity with fillermaterial, and then filling towards the posterior side of the cavity,fluids and/or suspended solids within the cavity are desirably displacedby the filler material and directed towards the posterior section of thecavity, where they can exit out the cannula. In this manner, “trapping”of fluids within the cavity and/or filler material is avoided and acomplete and adequate fill of the vertebral body is ensured.

If desired, the filler material can be allowed to harden and/or curebefore injection into the vertebral body. For example, in oneembodiment, the filler material comprises bone cement, which is allowedto cure to a glue or putty-like state before being injected into thecavity. In this embodiment, the cement would desirably have aconsistency similar to toothpaste as the cement begins to extrude fromthe nozzle.

The selected material 62 can also be an autograft or allograft bonegraft tissue collected in conventional ways, e.g., in paste form (seeDick, “Use of the Acetabular Reamer to Harvest Autogenic Bone GraftMaterial: A Simple Method for Producing Bone Paste,” Archives ofOrthopaedic and Traumatic Surgery (1986), 105: 235-238), or in pelletform (see Bhan et al, “Percutaneous Bone Grafting for Nonunion andDelayed Union of Fractures of the Tibial Shaft,” InternationalOrthopaedics (SICOT) (1993) 17: 310-312). Alternatively, the bone grafttissue can be obtained using a Bone Graft Harvester, which iscommercially available from SpineTech. Using a funnel, the paste orpellet graft tissue material is loaded into the cannula instrument 8430. The tamping instrument 124 is then advanced into the cannulainstrument 84 in the manner previously described, to displace the pasteor pellet graft tissue material out of the cannula instrument 84 andinto the cavity portion.

The selected material 62 can also comprise a granular bone materialharvested from coral, e.g., ProOsteon™ calcium carbonate granules,available from Interpore. The granules are loaded into the cannulainstrument 84 using a funnel and advanced into the cavity using thetamping instrument 124.

The selected material 62 can also comprise demineralized bone matrixsuspended in glycerol (e.g., Grafton™ allograft material available fromOsteotech), or SRS™ calcium phosphate cement available from Novian.These viscous materials, like the bone cement previously described, canbe loaded into the syringe 112 and injected into the cavity using thenozzle 114, which is inserted through the cannula instrument 84 into thecavity portion. The tamping instrument 124 is used to displace residualmaterial from the cannula instrument 84 into the cavity portion, asbefore described.

The selected material 62 can also be in sheet form, e.g. Collagraft™material made from calcium carbonate powder and collagen from bovinebone. The sheet can be rolled into a tube and loaded by hand into thecannula instrument 84. The tamping instrument 124 is then advancedthrough the cannula instrument 84, to push and compact the material inthe cavity portion.

The various instruments just described to carry out a bilateralprocedure can be arranged in one or more prepackage kits 126, 128, and130, as FIG. 23 shows. For example, a first kit 126 can package anaccess instrument group for achieving bilateral access into a singlevertebral body (comprising, e.g., at least one spinal needle instrument70, at least one guide wire instrument 76, at least one obturatorinstrument 78, two cannula instruments 84, and at least one drill bitinstrument 88). Alternatively, the first kit 126 can contain at leastone trocar 330 and two cannula instruments 84, which together form twocomposite instruments 310.

A second kit 128 can package a cavity forming instrument group for thebilateral access (comprising, e.g., two cavity forming tools 48). Athird kit 130 can package a material introduction instrument group forthe bilateral access (comprising, e.g., at least one syringe 112, atleast one nozzle 114, and at least one tamping instrument 124).Alternatively, the kit 130 can comprise a material introductioninstrument group comprising a syringe 112, a cannula 84 and a tampinginstrument 124 sized to fit within the cannula. The kits 126, 128, and130 also preferably include directions for using the contents of thekits to carry out a desired bilateral procedure, as above described.

A fourth kit 132 can also be included, to include the ingredients forthe filling material 62, which, as before explained, may contain apredetermined amount of a radiopaque material, e.g., barium or tungsten,sufficient to enable visualization of the flow of material 62 into thecavity portion. The kit 132 also preferably include directions formixing the material 62 to carry out a desired bilateral procedure, asabove described.

Of course, it should be understood that the individual instruments couldbe kitted and/or sold individually, with instructions on their use. Ifdesired, individual instrument kits could be combined to form procedurekits tailored to individual procedures and/or physician preference. Forexample, a general instrument kit for performing a single levelprocedure could comprise a guide wire instrument 76, an obturatorinstrument 78, a cannula instrument 84, and a drill bit instrument 88.

D. Alternative Cavity Formation and Filling Techniques

A cavity, filled with a compression-resistant material, can be createdwithin a vertebral body in alternative ways.

For example (see FIG. 24A), a small diameter expandable body 150 can beintroduced into a vertebral body through the stylus 72 of a spinalneedle assembly 70, or another needle sized approximately 8 to 11 gauge.Expanding the small structure 150 compacts cancellous bone to form adesired cement flowpath within the vertebral body and/or a barrierregion 152 substantially surrounding the structure 150. Alternatively, amechanical tamp, reamer, or single or multiple hole puncher can be usedto create a desired cement flowpath within the vertebral body and/orcompact cancellous bone to form a small barrier region 152. The desiredcement flowpath and/or compacted cancellous bone surrounding the barrierregion 152 will reduce and/or prevent extravazation of the flowablematerial injected outside the vertebral body.

A flowable filling material 154, e.g., bone cement, can be pumped underhigh pressure by a pump 156 through the needle 72 into the desiredcement flowpath and/or barrier region 152 (see FIG. 24B) in a volumethat exceeds the volume of the flowpath/barrier region 152. The fillingmaterial 154 pushes under pressure against the compacted cancellousbone, enlarging the volume of the flowpath/barrier region 152 asmaterial 154 fills the flowpath/region 152 (see FIG. 24C). The interiorpressure exerted by the filling material can also serve to move recentlyfractured cortical bone back toward its pre-fracture position. Theflowable material is allowed to set to a hardened condition, aspreviously explained.

A multiple level procedure can be performed using different treatmenttechniques on different vertebral body levels. For example, if a givenvertebral body layer has developed cracks and experienced compressionfracture, the cavity-forming and bone lifting techniques previouslydescribed can be advantageously used. The cavity forming and bonelifting technique can comprise use of one or more expandable largerbodies 56 followed by low pressure introduction of filling material (asshown in FIGS. 10 to 12), or use of one or more smaller expandablebodies 150 followed by high pressure introduction of filling material(as shown in FIGS. 24A to 24C), or use of a combination thereof (e.g.,in a bilateral procedure).

It may be indicated to treat another vertebral body utilizingvertebroplasty techniques, which have as their objectives thestrengthening of the vertebral body and the reduction of pain. Forexample, where the end plates of the vertebral body have depressed to apoint where an expandable structure cannot be safely inserted and/orexpanded within the vertebral body, bone cement can be injected underpressure through a needle directly into the cancellous bone of thevertebral body (without cavity formation). The bone cement penetratescancellous bone. To reduce flow resistance to the cement, the needle canpossess an increasing interior diameter, as shown in FIGS. 22A, 22B, or22C. The reduced flow resistance makes possible the use of more viscouscement, to thereby reduce the possibility that the cement will exudefrom the vertebral body.

Different treatment techniques can also be used in different regions ofthe same vertebral body. For example, any of the above describedcavity-forming and bone lifting techniques can be applied in one regionof a vertebral body, while conventional vertebroplasty can be applied toanother region of the same vertebral body. Such a procedure would beespecially well suited for treatment of scoliosis, as previouslydiscussed herein. Alternatively, the various disclosed techniques can beutilized in separate vertebral bodies within the same spinal column.

The features of the invention are set forth in the following claims.

We claim:
 1. A system for treating a bone, comprising: a device forcompacting cancellous bone comprising a wall adapted to be inserted intothe bone and undergo expansion in cancellous bone to compact thecancellous bone to create a cavity within the cancellous bone; a boneplugging material adapted to be inserted into cortical bone eitherbefore or after expansion of the device; and a filling material adaptedto be inserted into the cavity.
 2. A system according to claim 1,wherein the bone plugging material comprises a bone matrix material. 3.A system according to claim 1, wherein the bone plugging materialcomprises a sheet material.
 4. A system according to claim 1, whereinthe bone plugging material comprises a mesh.
 5. A system according toclaim 1, further including a device operable to convey the fillingmaterial into the cavity.
 6. A system according to claim 1, whereinexpansion of the device applies force within the cancellous bone capableof moving cortical bone.
 7. A system according to claim 1, furtherincluding a device operable to convey the bone plugging material intothe cortical bone.
 8. A system according to claim 1, further including adevice operable to convey a compression-resistance material into thebone.
 9. A system according to claim 1, further including a deviceoperable to convey medication into the bone.
 10. A system as in claim 1,wherein the plugging material guards against leaks.
 11. A system as inclaim 1, wherein the plugging material protects a weakened cortical bonewall during expansion.
 12. A system as in claim 1, wherein the pluggingmaterial protects against protrusion of the wall during expansionthrough a pre-existing breach in a cortical bone wall.
 13. A system asin claim 1, wherein the plugging material protects against protrusion ofthe wall during expansion through a breach in a cortical bone wallcreated during expansion.
 14. A method for treating a bone comprisingthe steps of: providing a device for compacting cancellous bonecomprising a wall adapted to be inserted into the bone and undergoexpansion in the cancellous bone to compact the cancellous bone;compacting the cancellous bone within the bone to create a cavity withinthe cancellous bone; inserting a bone plugging material into corticalbone either before or after the step of compacting the cancellous bone;and conveying a filling material into the cavity.
 15. A system fortreating bone, comprising: a device to compact cancellous bone to createa cavity within the cancellous bone; a bone plugging material adapted tobe inserted into cortical bone either before or after creation of thecavity; and a filling material adapted to be inserted into the cavity.